(1) Field of the Invention
This invention relates to an ink cartridge used for image forming apparatus such as a printer, a copier and a facsimile. This invention also relates to a detection device for identification of an ink cartridge, and to an image forming apparatus comprising the ink cartridge and the detection device.
(2) Background Art
Amongst conventional ink cartridges used for an inkjet recording apparatus, some of them are constituted to allow ink level detection by optical devices.
Generally, ink of this type of ink cartridge is reserved in a case having an optically transparent portion. Light is emitted from a light source to inside the case through the transparent portion. The amount of reflected light changes depending whether or not ink is remained in the ink cartridge. The presence of ink is detected by this system. Yoshiyama et al (Japanese Patent Publication No. 2002-292890), for example, discloses this type of ink cartridge.
In an ink level detection device for this type of ink cartridge, when there is plenty of ink reserved in an auxiliary ink reservoir of an ink cartridge, light emitted from a light emitter enters inside the ink cartridge, because the refractive index of the material constituting the ink cartridge and the refractive index of the ink are very close. Then the light is reflected toward a direction different from the direction toward a light receiver by a reflector disposed in the ink cartridge. Thus the amount of reflected light toward the light receiver is small.
When ink is not in the auxiliary ink reservoir, the light emitted from the light emitter is reflected between inside of an outer wall of the auxiliary ink reservoir and air (i.e. at a prism). The amount reflected light toward the light receiver, in this case, is large. As described above, the amount of reflected light from an ink cartridge changes depending whether or not ink is reserved therein, and the presence of ink is detected from the difference in the light amount by using a light receiver.
Recently, the consumption of ink has been increasing as more image formation is conducted by users on larger quantity of recording media. Ink cartridges containing large amount of ink have been on demand as a replacement for ink cartridges containing standard amount of ink, which is presently available. However, such type of ink cartridges are not yet attained and not supplied to the market.